1. Field of the Invention
The present invention relates to substrates for growth of plants, and methods of preparing and using such substrates. In particular, the present invention relates to substrates and methods for growing plants in contained environments, such as in containers in greenhouses, nurseries, private homes, or businesses.
2. Description of Related Art
The greenhouse and nursery industry in industrialized nations has seen strong growth in the last 40 years. In particular, container-grown plants have become an important part of the industry and an important aspect of home and office aesthetics. Growth of plants in containers, at least until they are introduced into a suitable final in-ground location, has become the standard method for supplying and maintaining many plants, including flowering plants, shrubs, trees, and the like, both in greenhouses and nurseries and in homes and offices. In view of the importance and scale of growing plants in containers, much time and research has been expended to develop and optimize growth conditions for growth of plants in containers. Most of the time and research has been focused on identifying suitable substrates, watering regimens, and amendments for growth of various plants.
Peat moss and softwood bark have provided the primary base for most greenhouse and nursery substrates over the last 30 years. These materials are excellent substrates but their future availability and cost is uncertain. For example, the environmental concerns of mining peat moss, which is a non-renewable natural resource found predominantly in the British Isles, Northern Europe, Scandinavia, and Canada, and the increasing costs of mining and shipping this substrate are factors that are predicted to significantly limit its availability and use in the future. In addition, although softwood bark is a renewable resource that appears to be satisfactorily available and properly managed at this time, the availability of softwood bark of consistent quality is often a problem due to the variety of methods used to harvest, process, and store bark. Furthermore, potential movement of the lumber and paper industry from the U.S. to other countries will likely limit the supply of softwood bark in the U.S., raising the question of future availability and further escalating the price of this substrate.
In recognition of the potential loss of peat moss and softwood bark as substrates for container plants, and in recognition of the escalating costs of these substrates over the years, many studies have investigated the use of various industrial and agriculture waste, such as animal waste (Tyler, et al., 1993b), cotton gin waste (Owings, 1993), wood by-products (Lunt and Clark, 1959, Chong and Lumis, 2000), municipal leaf and sewage sludge (Bugbee, et al., 1991, Rosen, et al., 1993), rice hulls (Dueitt et al., 1993), and residential refuse (Kahtz and Gawel, 2004) as substitutes for bark and peat moss. Most of these alternative substrate components show promise in that they are non-toxic to plants and can be successfully used to amend conventional substrates (i.e., peat moss, bark, soil, clay, and sand). However, a limited supply of a uniform and consistent quality product of each of these reduces their widespread use. Furthermore, none of these amendments have proved to be suitable as the sole substrate for growth of container plants.
Thus, there is a continuing need in the art for improved substrates for container plants. In particular, there is a need in the art for a relatively inexpensive, abundant, renewable substrate that can be used as the sole substrate, or as the main constituent of a substrate, for growth and maintenance of container plants.